Field of the Invention
The invention relates to a circuit configuration for voltage polarity reversal in a mobile radio transceiver for producing an output voltage having a polarity which is reversed with respect to an operating voltage.
The invention relates, in particular, to a circuit configuration in a mobile radio transceiver (for example mobile telephone) which is supplied with a battery voltage and produces a negative or positive voltage from a voltage which is positive or negative, respectively, with respect to a fixed reference potential.
In mobile radio transceivers which are supplied with a positive battery voltage and generally have one or more MMIC (Monolithic Microwave Integrated Circuit) chips (for example an MMIC power amplifier) on a MESFET basis, a negative gate bias voltage is required, for example, in order to operate the MESFETs. In a known circuit variant with which it is possible to produce a negative voltage in a battery-operated electronic device, an AC voltage having positive and negative voltage amplitudes is produced through the use of an oscillator or multivibrator and is subsequently rectified. In another circuit variant, it is possible to produce a negative voltage by rectification of a received radio-frequency signal applied to the input of an MMIC power amplifier.
However, those two methods have disadvantages. Thus, in the case of the option which was mentioned first, an additional AC voltage signal is produced by the oscillator in the mobile radio transceiver and can impair the operational properties of the device. It is possible, for example, for interference spectra to be modulated onto signals or for neighboring components in the mobile telephone, such as microprocessors, for example, to be influenced and consequently impaired.
In the case of the method which was mentioned second, the fact that the MMIC power amplifier is turned on only after application of the radio-frequency signal and is functional only at relatively high signal levels, turns out to be particularly disadvantageous.